Technology and Business of HPHT Treatment

Abstract

Technological principles, instrumentation and parameters of HPHT annealing used for commercial treatment of natural diamond are discussed. The emphasis is made on the description of design of high pressure cell and the methods of measurement of pressure and temperature during HPHT treatment. The preparatory procedures the diamonds undergo before HPHT annealing are discussed in detail. These procedures comprise selection of diamonds, their pre-shaping, cleaning and initial characterization. Examples of failure of HPHT treatment caused due to neglecting to follow the technological protocol are presented. Basic processes of the defect transformations and the color changes in brown diamonds of different color intensity and different type during HPHT treatment summarized and discussed. Commercial aspects of HPHT treatment, including the present state of the market of yellow-green and pink-red treated diamonds, cost of HPHT treatment and the final prices of HPHT-treated diamonds, are discussed.